1. Field of the Invention
The invention relates to a semiconductor storage device and a method of controlling the semiconductor storage device, and is particularly suitable for use in a semiconductor storage device using an electrically rewritable non-volatile memory as a storage medium and a method of controlling the semiconductor storage device.
2. Description of Related Art
A semiconductor storage device in which data in a logical block is distributed to plural flash memory physical blocks to be stored, and when the data stored in each of the physical blocks is updated, the relevant update data is recorded in a blank page in the physical block, and the original stored data is invalidated; and in which, if the physical block lacks a blank page, latest update data in the physical block is merged into the stored data and the resultant data is copied to another physical block, a new blank page is reserved, and subsequent update data is recorded in the blank page is a known storage device (see e.g., U.S. Pat. No. 7,039,788). Note that “merge” means that an old piece of data is replaced by the latest piece of data to build the latest data.
Also, a method of managing virtual blocks for a semiconductor storage device provided with plural flash memory chips and in which physical blocks in the respective chips are assembled into virtual blocks and read/write to the chips is conducted via parallel processing is known (see e.g., JP2006-127234 A).
When a control method in which blank pages in a physical block are utilized to record update data, which is as shown in U.S. Pat. No. 7,039,788, is utilized in the semiconductor storage device provided with plural flash memory chips, and the chips are subjected to parallel processing to improve performance, which is as shown in JP2006-127234 A, the parallel processing involving the chips may be executed inefficiently, due to the recorded state of the update data, leading to deterioration in write/read performance.